The present invention relates generally to an internal combustion engine. The present invention also relates to a device and method for starting the internal combustion engine, and, more specifically, to an engine starting device that is capable of storing energy in an elastic member and then releasing the energy to start the engine. The present invention also relates to a device and method for stopping the internal combustion engine or, at least, for absorbing energy of the engine upon shutdown. The engine starting device is particularly adapted for use with small internal combustion engines such as those provided on power lawn mowers, generators, snow blowers, garden tractors, and other machinery.
Small internal combustion engines have been equipped with manually operable recoil starters which include a central shaft, a rope pulley rotatable about the central shaft, retractable clutches or dogs connected to the rope pulley and a starter rope wrapped around the rope pulley. The starter rope may be pulled to rotate the rope pulley in a starting direction, such that the dogs engage the flywheel, and the flywheel and the crankshaft are also rotated in a starting direction. The engine is then driven through a number of revolutions sufficient for starting.
Although recoil starters of the type described above are commonly used with small internal combustion engines, there are certain disadvantages inherent in their operation. For example, the operator must possess a sufficient amount of strength and manual dexterity to pull the starter rope to rotate the flywheel and crankshaft. Under some conditions, the operator may have to pull the starter rope several times before the engine is successfully started. For some operators, this is a mere inconvenience. For other operators, including the elderly and the physically challenged, pulling a starter rope multiple times may present a difficult task.
An alternative to recoil starters and other manual starters are automatic starters which include a battery-powered electric motor for driving the flywheel through initial starting revolutions. Such a starter may be actuated by merely activating an electrical switch in the form of a push button or key device. Although this concept provides an engine starting device that is both easy to operate and generally effective, the electric motor, the battery used to power the motor, and associated components can add weight and cost to an engine. For small internal combustion engines such as those intended for use with lawn mowers, generators, and like machines, adding even a small amount of weight and cost to the engine can negatively impact the market competitiveness of the engine and/or the machine.
Another type of automatic starter is an engine starting device that utilizes stored energy in a spring to rotate the crankshaft and to start the engine. In these engine starting devices a mechanism must be provided to wind the spring. For example, U.S. Pat. No. 1,936,554, which is assigned to Briggs and Stratton Corporation (the assignee of the present invention) discloses an electric motor that is positioned adjacent the spring and which may be operated to wind the spring. It is also known to provide a manual crank mechanism interconnected with the spring and operable to wind the spring. Further, it is known to provide a winding mechanism interconnected with the crankshaft that is operable to wind the spring during normal engine running conditions.
In an internal combustion engine having a rotatable engine assembly or member, such as an assembly comprising a crankshaft, flywheel and output device (e.g., a cutting blade), the rotatable engine member contains kinetic energy due to its angular momentum after the engine ignition is shut-off by an operator. In some applications, the angular momentum is sufficient to move the rotatable engine member through multiple revolutions. A general feature and advantage of the present invention is a device or mechanism for utilizing the energy inherent in a rotatable or rotating engine member or assembly of a small internal combustion engine after the operator initiates shutdown of the engine (e.g., by operating a switch in a magneto or battery ignition system). More particularly, it is a feature and an advantage of the invention to provide, in such a mechanism or device, an engine starting device adapted for use with small internal combustion engines, and alternatively, to provide a machine that incorporates such an engine starting device.
For purposes of description, the terms xe2x80x9cshutdownxe2x80x9d and xe2x80x9cshut-offxe2x80x9d shall apply to the operation of a switch in the ignition system or an equivalent mechanism to turn the engine off. These terms shall also apply to any operation that effects the same result. The term xe2x80x9cengine coast downxe2x80x9d shall apply to the condition, status, or phase of the engine and/or rotatable engine member after engine xe2x80x9cshutdownxe2x80x9d or xe2x80x9cshut-offxe2x80x9d is initiated, but before the rotatable engine member ceases movement or rotation.
It is yet another feature and an advantage of the invention to provide a mechanism for braking a rotatable engine member upon engine shutdown, wherein the energy of the rotatable engine member is absorbed and/or stored by the braking mechanism.
It should be noted that, in the United States and other countries, a device is required on lawn mowing machines for arresting the rotation of the cutting blade within a specific time period after the operator initiates engine shutdown. Typically, the cutting blade is connected to the crankshaft such that it stops rotating at the same time that the engine stops reciprocating. Accordingly, a brake mechanism may be applied to the flywheel during engine shutdown to arrest rotation of the cutting blade. The braking mechanism of the present invention is also adapted for such an application.
In one aspect of the invention, the engine starting device includes an energy storing mechanism, an input element, and an output element. The energy storing mechanism includes at least one elastic member. The input element is engageable with the elastic member and movable during engine coast down to load the elastic member to a loaded state (e.g., by compressing, stretching, or flexing the elastic member). The output element is movable in response to the energy storing mechanism as the elastic member unloads from the loaded state. In this way, the output element moves or rotates the rotatable engine member in a starting direction, thereby driving the engine through initial engine revolutions sufficient for starting.
The engine starting device may also include an input control device for positioning the input element in engagement with the rotatable engine member such that the input element is movable by the rotatable engine member to load the elastic member. In one embodiment, the input element includes a rotatable input member (e.g., a friction roller or gear) movable by the input control device between a first position and a second position. In the first position, the rotatable input member is rotatably engageable with the rotatable engine member. The input member may be adapted to engage different portions of the rotatable engine member including the crankshaft, the flywheel, a ring gear attached to the flywheel, or a starter-type cup interconnected with the crankshaft. When disposed in the second position, the rotatable input member is rotatably disengaged from the rotatable engine member. Further, the engine may be equipped with an engine control device actuable to initiate shutdown of the engine. In this case, the input control device may be operatively connected with the engine control device such that the input control device is actuated to position the input element in engagement with the rotatable engine member whenever the engine control device is actuated.
In one particular embodiment of the invention, the input control device includes a manual actuator (e.g., a push button or deadman bail handle), a control cable, a pivotable housing supporting the input element, and a control cable and lever interconnecting the manual actuator with the pivotable housing. The input control device may also be interconnected with an ignition system grounding or shut-off switch. Upon actuation of the manual actuator, the pivotable housing is pivoted toward the rotatable engine member such that the input element rotatably engages a portion of the rotatable engine member (e.g., the flywheel or a ring gear attached to the flywheel).
The energy storing mechanism may also include a drive member engageable with the elastic member. The drive member is movable in a first direction by the input element to load the elastic member and movable by the elastic member in a second direction, as the elastic member unloads from the loaded state, to move the output element. Preferably, the drive member is a rotatable member such as a shaft, a rotatable housing, or an annular member rotatably mounted about a shaft. In one embodiment, the drive member includes a rotatable shaft portion or hub having a rotational axis and the output element is mounted for rotation about the rotational axis. In another embodiment, the drive member and the elastic member are spaced axially from the crankshaft and the flywheel, whereby the rotational axis of the drive member is disposed substantially coincidental with a rotational axis of the flywheel or crankshaft.
The engine starting device may also include unidirectional transmission means (e.g., a clutch assembly or a combination helix shaft and axially-movable pinion gear) for rotatably engaging the output element with the rotatable engine member. When the drive member rotates in the second direction, the transmission means allows for the output element to be driven and to rotate the rotatable engine member in the starting direction. However, when the drive member rotates in the first direction, the output element and the rotatable engine assembly are rotatably disengaged.
In one particular embodiment of the invention, the engine includes a recoil starter having a recoil spring, a recoil pulley operatively connected with the recoil spring, and a central driving element (e.g., a starter hub) rotatable in a driving direction by the recoil pulley to drive the rotatable engine member in the starting direction. A drive member of the engine starting device is mounted about the central driving element and rotatable by the elastic member to drive the central driving element in the driving direction.
The elastic member may include at least one windable spring disposed about and/or interconnected with a drive member. In alternative embodiments, the elastic member can have different configurations (e.g., a compressible spring) or may be formed from other elastic materials (e.g., rubber or synthetic material). In one embodiment, the energy storing mechanism includes a housing mounted for rotation (e.g., about the crankshaft or a drive shaft of a recoil starter) and the elastic member is substantially disposed within the housing. One portion of the elastic member is interconnected with the housing while another portion is interconnected with the support member (i.e., a stationary flange).
In one particular embodiment of the invention, the engine starting device includes a rotatable input element, a rotatable output element, a manually releasable locking mechanism, an input control device, and an energy storing mechanism having an elastic member. The energy storing mechanism also has a rotatable drive member that is interconnected with the elastic member. The drive member is rotatable in a first direction to wind the elastic member to a loaded state and rotatable in a second direction by the elastic member as the elastic member unwinds from the loaded state. The rotatable input element is provided to engage with the drive member and to rotate the drive member in the first direction. The input control device is operable to position the input element in rotational engagement with the rotatable engine member during engine coast down such that the drive member is rotatable by the input element in the first direction. Further, the rotatable output element is rotatable in at least one output direction by the drive member when the drive member is rotated in the second direction. Rotation of the output element in the output direction results in the rotatable engine member being rotated in the starting direction.
Finally, the manually releasable locking mechanism is engageable with the energy storing mechanism to prevent the elastic member from unloading from the loaded state and rotating the output element. The locking mechanism may include a manual actuator remotely disposed from the engine and operable to release the locking mechanism and to initiate unloading of the elastic member from the loaded state. In one form of the invention, the locking mechanism includes a pawl member and a movable member (e.g., a ratchet wheel) interconnected with the energy storing mechanism. The movable member is equipped with a ratchet surface and the pawl member is adapted to engage the ratchet surface and to restrain movement of the movable member manually-operable key device may be provided for locking the pawl member in an engaged position with respect to the movable member.
A braking mechanism according to the invention generally includes an energy absorbing mechanism, an input element, and an input control device. The energy absorbing mechanism includes at least one elastic member and the input element is engageable with the elastic member and movable to load the elastic member to a loaded state. The input control device is actuable to position the input element into engagement with the rotatable engine member such that rotation of the rotatable engine member moves the input element to load the elastic member.
A manually operated machine according to the invention generally includes an internal combustion engine having a rotatable engine member, a manually actuable engine control device for initiating shutdown of the engine (e.g., by operating a bail handle, push button, or safety stop switch for the ignition system), and an engine starting device. The engine starting device includes an energy storing mechanism having at least one elastic member, an input element that is movable to load the elastic member to a loaded state, and an output element movable in response to the energy storing mechanism as the elastic member unloads from its loaded state. Also provided is an input control device for positioning the input element into engagement with the rotatable engine member. When the engine control device is actuated to initiate shutdown of the engine, the input element is then movable to load the elastic member.
Another feature of the invention is a means for preventing the input element from further loading the elastic member after the elastic member is loaded past a predetermined loaded state. If the elastic member includes a windable spring or band, the preventing means functions to prevent overwinding of the spring or band. In one form, the preventing means includes a slip clutch assembly operatively positioned between the input element and the elastic member. In another form, the preventing means includes a frictional brake engageable with the drive member or another component of the energy storing mechanism or energy absorbing mechanism.
Another feature and an advantage of the present invention is to provide an engine starting device that is simple in construction and easy to operate.
Yet another feature and advantage of the present invention is to provide an engine starting device that is lightweight and does not add considerable cost to the overall cost of the engine.
Yet another feature and advantage of the present invention is an engine starting device that is particularly adapted for retrofitting onto an existing small internal combustion engine.